Evidence for the Oldest Eukaryotic Life Found

Yuangao Qu, a post-doc at the Centre for Geobiology (CGB), was a member of a team who discovered macroscopic fossils from the 1 560 Myr old Gaoyuzhuang Formation in the Yanshan area of North China. The results have been published in Nature Communications.

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Nature Communications

Published: 21.05.2016

The article explains that discoveries of macroscopic eukaryote fossils rarely date to earlier than the Ediacaran Period (635–541 million years (Myr) ago). In addition, their interpretation remains controversial as both their cellular structure and phylogenetic affinities remain uncertain.

Macroscopic multicellularity may have evolved early in the eukaryotic domain

The newly discovered fossils provide the strongest evidence yet that multicellular eukaryotes with deci-metric dimensions and a regular developmental program populated the marine biosphere at least a billion years before the Cambrian Explosion (542 Myr ago). They indicate that simple macroscopic multicellularity evolved early in the eukaryotic domain.

The fossils consist of an assemblage of large and unusually well-preserved carbonaceous compressions from the lower Mesoproterozoic ( 1 600 – 1 000 Myr ago), Gaoyuzhuang Formation in the Yanshan area, North China. Their morphology differentiates the fossils from contemporaneous or younger structures formed by the reworking of microbial mats. They are large (decimetre-scale) in size and regular, and are strongly elongated. They more closely resemble macroscopic eukaryotic organisms, especially benthic algae, observed today and in younger rocks. As yet, the phylogenetic placement of these remains is uncertain.

Early Mesoproterozoic eukaryotes

The researchers conclude that these Gaoyuzhuang fossils represent a modest diversity of macroscopic multicellular eukaryotic organisms that lived in shelf areas of early Mesoproterozoic oceans. They provide the most compelling evidence yet reported that eukaryotic organisms had evolved macroscopic form, multicellularity with limited cell differentiation, and (probably) photosynthesis by the beginning of the Mesoproterozoic Era, 1,600 Myr ago.

Such rare pre-Ediacaran (>635 Myr) fossils may reflect processes of preservation rather than simple biological absence. The researchers speculate that continuing research will provide new insights into marine ecosystems in the low oxygen world, and that this may not, in fact, be a ‘boring billion’ year interval in terms of its evolutionary as well as environmental stability.